Intermediate thermomechanical analysis and optimization of the ITER Upper port mounted bolometer camera

Abstract

The bolometer diagnostic system in the ITER monitors the plasma radiation from multiple positions inside the vacuum vessel for a complete measurement. The cameras are named according to their locations, like the port plug (PP) cameras and the divertor ones. This paper is about the cameras in the upper port plug. Because of the severe working environment, especially the high neutron and gamma heating power and the electromagnetic (EM) forces during the plasma disruptions, the camera structure has two functions: 1) in the thermal point of view, the heat deposited on the sensors needs to be effectively exhausted; 2) in the structural point of view, the camera must keep in position under various of mechanical loads.

Due to limited space, passive cooling methodology is chosen, in which the camera housing conducts the heat to the Diagnostic Shield Module (DSM), so a thick metallic housing is helpful in both neutron shielding and heat conduction. However, during disruptions these thick walls will induce strong eddy currents and cause high EM forces. Additionally, the mechanical constraints, in order to resist these dynamic EM loads, generate high thermal loads on the camera. Therefore, the design optimization must carefully find a balance among all relevant issues.

The port plug design has been finished and provides the attachment boundary conditions for the camera analysis, but the information is not detailed enough, then the camera finite element (FE) model is integrated into the existing PP FE model for a seamless interface. The methodology and intermediate results of the thermomechanical analysis are presented, and the experience gained are also applicable for similarly attached in-vessel components.